6711 hot pto lever?

[grumpy6711]

hi folks
got the topper out for the first time this year today and put it to good use. nice hot sunny day so doors off and away i went.
towards the end of the afternoon i noticed the pto selector lever (the on /off one by the hand clutch not the 540/1000 one under the seat) got quite hot (and stiff). I am assuming this is because the hyd. fluid got rather warm.
is this normal?
its only a 4 ft topper, but the grass was a touch on the long side (2-3 ft) and it wasnt struggling. tractor temp did creep out of the green but again no problems.
anything i need to keep an eye on or look out for?

 

[Renze]

transmissions must stay under 70 degrees to keep proper lubrication and oil film thickness on gears. If you can keep your hand on the transmission for 10 seconds, its probably less than 50 degrees.
If we install an oil cooling kit on a wet brake axle, the fan starts at 55 degrees in order to keep it under 70 degrees.

 

[grumpy6711]

I had to use a rag over the lever as it was too hot to hold - which i'm guessing is not as it should be
could it possibly be incorrect oil? i use what the guy in the shop said was ok for a zetor , but they are MF dealers, so i have MF fluid, 15w30 ? i think?

 

[hve]

Hi Grumpy,
I would expect the case to get too hot to touch but not the leaver so something is amiss.
It is possible that the 80W90 oil Zetor specify would run cooler as it has special additives in it to increase lubricity for gears.
I am not familiar with the MF oil so cannot comment on what is in that...... i assume similar to UTO? But if it is just hydraulic oil then it does not have the required lubricity additives for a transmission.

Sounds like most of the work pulling and driving the topper was being done by the transmission including PTO gears and Diff, none of which have anything to do with the hydraulic pump ..... unless something is stuck and the hydraulics were under full pressure out the relief valve the whole time.......... you didn't by chance still have the outer circuit lever tied back for using the log splitter? ...... i assume the pto speed was set to 540 and not 1000

The fact that the lever got stiff is of concirn, as this suggests lack of lube, and or something inside was so hot that it was messing with the clearances or alignment of the selector levers.
All the selector rods are next to each other in the top cover..... Did the gear leaver, or Hi Low ratio lever feel any stiffer than usual? Or just the PTO/Pump leaver
Question: what setting did you have it in while topping? (ie 540 or Ground speed)

Might be a good idea to fit a oil temp gauge if the problem is not identified, you dont want to fry the oil.

 

[askinner]

unless something is stuck and the hydraulics were under full pressure out the relief valve the whole time.......... you didn't by chance still have the outer circuit lever tied back for using the log splitter? ...... i assume the pto speed was set to 540 and not 1000

I agree, sounds like the hydraulics may have been going over the relief the whole time, this would make the oil red hot very quickly!

 

[grumpy6711]

unless something is stuck and the hydraulics were under full pressure out the relief valve the whole time.......... you didn't by chance still have the outer circuit lever tied back for using the log splitter? ...... i assume the pto speed was set to 540 and not 1000

I agree, sounds like the hydraulics may have been going over the relief the whole time, this would make the oil red hot very quickly!

.................................................erm...possibly 69)
hedge trimmer was the last imp used - i will check later.
cheers guys

 

[grumpy6711]

Its official. I AM A MUPPET!
yes! i had the outer circuit lever locked forward
so now its floating in neutral and everythings a lot quieter and hopefully cooler.
lesson learned.
Thanks for the info

 

[askinner]

Renze, as a point of interest, I work on mining equipment, our Cat 793 trucks hydraulic system runs at around 88c without braking (engine thermostat temp), generally runs around 95-110 while braking, warning starts at 124c. The brakes are cooled by the hydraulic oil, hyd oil is cooled with engine jacket water. Only use standard mineral 30W hyd oil. Wouldn't want to run my 7245 at those temps with Zetor seals though, they'd be rock hard after a few hours!

 

[hve]

Renze, as a point of interest, I work on mining equipment, our Cat 793 trucks hydraulic system runs at around 88c without braking (engine thermostat temp), generally runs around 95-110 while braking, warning starts at 124c. The brakes are cooled by the hydraulic oil, hyd oil is cooled with engine jacket water. Only use standard mineral 30W hyd oil. Wouldn't want to run my 7245 at those temps with Zetor seals though, they'd be rock hard after a few hours!

Yeiks, thats getting up there....... but then engine oil generally runs at 90-120 Deg.C ..... you quickly get Varnish build up above 140Deg.C

As a matter of interest....
As a rule of thumb, any chemical reaction (including oxidation, or curing of a 2 pack epoxy) will increase speed with change in Temperature, by a factor of 2 for every 10 Deg.C increase

To put this into practice:
If hydraulic oil is burnt out (oxidised) after 200hrs at 100Deg.C, the same oil in the same conditions, (other than temp) will last 400hrs at 90 Deg.C, but only 100hrs at 110Deg.C, 50hrs @ 120Deg.C etc.

Other factors that influence oxidation of oil is:

1. Exposure to O2: The greater the surface to volume ratio the quicker the oil will oxidise......... Foaming is BAD as there is a massive O2 to oil ratio produced! more foaming occurs in a tractor gearbox than a simple hydraulic circuit, as the gearbox is generally not fully immersed in the oil and air is entrained in by the gears, thus a simple hydraulic set up will work fine at >120Deg.C as there is very low exposure to Air, but a tractor transmission will quickly kill the oil at >120Deg.C

2. Free Radicals: These are produced as part of the oxidation process and "attack" the good molecules of oil, thus the more oxidised (burnt) the oil is, the quicker it will degrade (oxidise more)
Anti-oxidants (additives such as BHT or Irganox) are used in some oils to prevent (or rather "slow") oxidation at elevated temps, however they are mostly sacrificial and are eventually all used up.

Chemistry lesson endith

 

[askinner]

It never ceases to amaze me we change the hyd oil on these trucks at 2000hrs, sometimes 4000hrs with 10W oil as per Cat's recommendation (oil samples generally show it is still perfectly fine at drain time though). The oil will generally hit 100-110c every 20 minutes (avg haul cycle) keeping a 400 tonne of truck under control 22hrs a day, 7 days a week. What is a major problem, is when a hyd oil cooler fails, and lets coolant in the hyd system, it swells the brake material, causing drag. I've seen temps around 148 c when this happens!! Operators not using the automatic retarding system are the biggest cause of warped brake dics though. Man will never be as precise as a computer!

 

[askinner]

Other factors that influence oxidation of oil is:

1. Exposure to O2: The greater the surface to volume ratio the quicker the oil will oxidise......... Foaming is BAD as there is a massive O2 to oil ratio produced! more foaming occurs in a tractor gearbox than a simple hydraulic circuit, as the gearbox is generally not fully immersed in the oil and air is entrained in by the gears, thus a simple hydraulic set up will work fine at >120Deg.C as there is very low exposure to Air, but a tractor transmission will quickly kill the oil at >120Deg.C

This is also multiplied by a tractor's transmission, as the air in suspension is heated when the hyd system compresses it, generating further oxidisation, and more importantly, cavitation in the hyd pump.

 

[Renze]

Have you ever seen wet brake axles of which the paint on the housing turned black from the heat ?? Thats what we get with payloaders in load&carry operations in seaports... It would meet temperatures generally used in frying pans: You could make fish&chips in the oil. Or for the Dutch guys: fry a frikandel in it. So now we put coolers on them.

The oil that comes off the torque converter hits 120 degrees in stall conditions, but it should stay under 90 degrees when it comes out of the cooler and flows back to the transmission sump..

But a tractor transmission is different to a converter transmission and therefor, generally isnt built for these oil temperatures.

Next to that, a loader transmission that gets 100 degrees every day, wont deteriorate as much as a tractor transmission that gets hot once a month, and the rest of the month is catching humidity from the air without vapourising it because it wont get that operating temperature so often...

 

[grumpy6711]

update!
ran the topper again for four hours today, and not only did the lever not become even slightly warm, you could quite happily rest your face on the transmission block (if you were that way inclined), just nicely warm.
so thanks again for the heads up guys.

Skin - are you by any chance in the big pit in Kalgoorlie-Boulder?
a mate of mine worked there for a few years on the big spanners and i stopped by for a few days. a strange place with some interesting sights and a distinct lack of women (not counting Hay St!) but that was 10 or 15 years ago so maybe its changed?

 

[askinner]

Hi Grumpy, glad to hear it's fixed! Good thing the oil runs a bit of warmth, helps keep the water out. The breather setup on these is the worst idea, a hole in the gearstick boot, ok if it has a cab and you don't wash it out, but on a open tractor, you need to be careful not to hose the gearstick area and fill it up with water.
No, I'm in the Hunter Valley, New South Wales. We mine coal around here, not as tough as those hard rock miners, but still a shortage of lady folk , though we have a lot of girls driving the trucks these days

 

[Renze]

not as tough as those hard rock miners, but still a shortage of lady folk , though we have a lot of girls driving the trucks these days

That means that the girl drivers wouldnt qualify as "lady folk" ??

 

[askinner]

Renze, unfortunately there are a few, but still few and far between! They also end up not so lady like after a couple of years knocking round with the blokes!! Swear like troopers, and end up with no shame doing their "business" behind a trucks tyre....